Annual Residence Time Drives Sediment Nitrogen Concentrations in Reservoirs Using Paleolimnological Techniques
Reservoirs are hotspots for sediment and nutrient deposition. However, less is known of how reservoir nitrogen (N) deposition is altered at the watershed scale. In this study, we compared average annual hydrologic residence time (RT) along with other physical parameters to the sediment N concentrations for eight reservoirs in the SE USA. RT is determined by water storage in a reservoir and dam release rate and can be linked to dynamic processes like trap efficiency. The eight reservoirs varied regarding RT, surface area, water volume, land use, catchment area, primary usage (hydropower and storage), and other parameters. Using long-term reservoir flow data, federal long-term drought indices, GIS tools, and paleolimnological techniques, average annual RT was found to have the strongest relationship with sediment N concentrations (R2 = 0.79) when compared to all other reservoir parameters. RT drives N deposition by allowing longer periods of algal growth followed by deposition of N in particulate organic form. Photosynthetic pigments supported this inference and identified cyanobacteria being the primary producer group most related to RT (R2 = 0.73) followed by diatoms (R2 = 0.56). In periods of drought, basin managers are forced to abide by critical yields and base flow regulations to maintain reservoir water storage thus increasing water retention times. Following our sediment and RT based model, during these extreme long-term drought periods, RT increased by 45 – 60% increasing N delivery to the sediments by roughly 2.5 – 4%.
Primary Presenter: Benjamin Webster, Auburn University (benjcwebster@gmail.com)
Authors:
Benjamin Webster, Auburn University (bcw0030@auburn.edu)
Matthew Waters, Auburn University (mwaters@auburn.edu)
Stephen Golladay, Albany State University (steve.golladay@jonesctr.org)
Annual Residence Time Drives Sediment Nitrogen Concentrations in Reservoirs Using Paleolimnological Techniques
Category
Scientific Sessions > SS23 - Dynamics of Reservoir Ecosystems in the Anthropocene: Ecology, Biogeochemistry, and Physics
Description
Time: 02:45 PM
Date: 5/6/2024
Room: Meeting Room MN